A related X-ray dual-energy CT (Computed Tomography) imaging technique decomposes an attenuation coefficient function of a substance into a linear combination of attenuation coefficient functions of two known basis materials, and coefficients of the linear combination are unknown parameters to be solved. The decomposition of a scanned object uses a fixed set of double basis materials and a corresponding fixed set of attenuation coefficient functions. For example, water and bone can be selected as double basis materials in medical dual-energy CT.